Illumination systems for generating high brightness illumination are interesting for various applications including spots, stage-lighting, headlamps and digital light projection.
High brightness light with a desirable spectral distribution may be obtained by a system 1, see FIG. 1, using a bright light source 10 such as a light emitting diode, LED, or a laser where a high intensity light beam of a first wavelength 15 (e.g. blue light) emitted by the light source is directed towards an optical device comprising a light converting member 20 placed on a static heat sink 30. A dichroic reflector 40 is arranged to selectively reflect the light of the first wavelength 15 towards the optical device. Hence, the light converting member 20 is illuminated with a focused beam of light of the first wavelength 15. Light of the first wavelength 15 is partially converted to light of a second wavelength 25 (e.g. yellow light) by the light converting member 20. White light is obtained when light of the first and second wavelengths are mixed.
In such a setup, in order to achieve good heat dissipation from a phosphor light converting member combined with a high luminous efficiency, US20140166902A1 discloses a wavelength conversion body comprising a light guide body being monolithically connected to the phosphor body. Extending such construction for further improvement of heat dissipation, US20050270775A1 discloses a system, in so far similar to the one shown in FIG. 1, spatially separating the light source from the phosphor by a color separation element, as e.g. dichroic reflector 40 of FIG. 1, for prohibiting converted light returning to the light source.
However, such dichroic reflector 40 reduces the intensity of the first light wavelength 15 emitted by the system. Moreover, the dichroic reflector also affects the color of the combined light. Furthermore, in the arrangement the lens 35 used for focusing and collecting the converted light 25 is not efficient enough to collect all the emitted light.